My name is Maria, and I'm Agnes daughter. Agnes is John's grandniece, and lived in Tanganika till the age of 11. Her father Robert (Barrhead, Scotland) went there in order to work for his uncle John at his farm, and took his wife with him. Their 3 daughters were born there (being my mum the oldest).
I'll tell my mum about this forum so she can contact you and tell you everything about her grand-uncle John. He loved her very much, as he never had any children of his own. And she's also investigating about her family history, so I think she'll be glad to talk to you about it.
Please excuse any grammar mistake, I'm Spanish -my mum taught me the English I know -